The present invention relates to an image processing apparatus and method, more particularly, to an image processing apparatus and method capable of forming an image in at least two colors collectively before transferring to a recording medium.
Conventionally, a two-color digital copy machine is available as an image processing apparatus capable of forming an image in two different colors, such as black and red, collectively.
In the conventional two-color digital copy machine, a photoelectric converter, such as a color CCD, scan a color original image as RGB signals. And the RGB signals are converted to CMYK signals. Then, an image area is recognized and separated from the CMYK signals, and image data for forming a latent image for a first color and image data for forming a latent image for a second color are generated from the separated image area. Thereafter, the latent image of image data corresponding to the first color is formed on an electrostatic drum by using a laser beam, and a latent image of image data corresponding to the second color is formed on the same electrostatic drum over the latent image for the first color. By transferring the two latent images for two colors formed on the single electrostatic drum at once, an image of two color is visualized on a recording medium.
In the aforesaid two-color digital copy machine, since the latent image for the second color is formed over the latent image for the first color, the second color is not reproduced in its original color because of a light-shielding effect of the latent image for the first color which is exposed in prior against a laser beam. Thus, the colors are not mixed properly, which causes the deterioration of quality of an image.
Therefore, in the two-color digital copy machine, a method for correcting density values of image data of the second color is suggested by U.S. patent application Ser. No. 08/312,937 in order to solve the problem in which the second color is deteriorated. For example, a method to increase the density value of the second color in accordance with a predetermined ratio or a ratio corresponding to the density value is suggested. On the contrary, a method to decrease the density value of the first color in accordance with a predetermined ratio or a ratio corresponding to the density value is suggested. Then, by forming latent images for each color in accordance with the corrected density values, the deterioration of the second color is prevented. However, it has not been possible to preserve density ratio of a density value of the first color to that of the second color and to preserve the density values of both the first and second colors together at one time, when the correcting method for the second color is applied to the conventional two-color digital copy machine.